Risk factors for Clostridium difficile colonisation and toxin production.

Objectives: to examine risk factors for patients becoming Clostridium difficile culture and toxin positive.

Design: prospective cohort study.

Setting: two medicine for the elderly wards.

Participants: patients admitted to the wards over a 17-month period.

Measurement: presence of Clostridium difficile on culture of stool specimens and toxins A and/or B. Patient's age, sex, source of admission, antibiotic, laxative, antacid and steroid use, presence/absence of colonic disease, neoplasia, leukaemia and nasogastric or percutaneous endoscopic gastrostomy tube feeding.

Results: 390 of 865 patients admitted provided a total of 1003 faecal specimens. Age (OR 1.04, 95% CI 1.001-1.07 per year), admission from another hospital (OR 2.13, 95% CI 1.29-3.50), non-cephalosporin antibiotics (OR 2.08, 95% CI 1.25-3.46) and cephalosporin use (OR 8.45, 95% CI 2.99-23.9) increased risk of becoming Clostridium difficile culture positive. Becoming toxin-positive was associated with antibiotic use only (OR 3.02, 95% CI 1.15-7.92), specifically amoxycillin (OR 8.72, 95% CI 1.66-45.9) and cephalosporins other than ceftriaxone (OR 7.28, 95% CI 1.34-39.6).

Conclusion: different risk factors are important for the two stages leading to Clostridium difficile diarrhoea. Age, source of admission and third generation cephalosporins increase risk of becoming culture positive, whilst only antibiotic use is associated with the step of becoming toxin-positive. Understanding these differential risks may aid infection control strategies.